In this work the design and initial fabrication results are reported for the components of a compact optical-MEMS laser scanning system. This system integrates a silicon MEMS laser scanner, a Vertical Cavity Surface Emitting Laser (VCSEL) and passive optical components. The MEMS scanner and VCSEL are mounted onto a fused silica substrate which serves as an optical interconnect between the devices. Two Diffractive Optical Elements (DOE's) are etched into the fused silica substrate to focus the VCSEL beam and increase the scan range. The silicon MEMS scanner consists of an actuator that continuously scans the position of a large polysilicon gold- coated shuttle containing a third DOE. Interferometric measurements show that the residual stress in the 50 micrometer X 1000 micrometer shuttle is extremely low, with a maximum deflection of only 0.18 micrometer over an 800 micrometer span for an unmetallized case and a deflection of 0.56 micrometer for the metallized case. A conservative estimate for the scan range is approximately plus or minus 4 degrees, with a spot size of about 0.5 mm, producing 50 resolvable spots. The basic system architecture, optical and MEMS design is reported in this paper, with an emphasis on the design and fabrication of the silicon MEMS scanner portion of the system.

A compact two-mirror microscanner has been fabricated to build the central part of a miniaturized confocal laser scanning microscope. This microscope shall be mounted at the tip of an endoscope to provide high resolution imaging for medical diagnostics. In order to achieve a resolution of 500 X 500 image elements large scan angles and also large mirror dimensions have to be realized within a spatially strong limited housing. While bulk silicon technology on the one hand enables fabrication of micromirrors with nearly ideal elastical behavior, those actuators on the other hand often are too fragile for a lot of applications. This paper describes the design, fabrication and assembling of electrostatically driven torsional micromirrors that meet the requirements of fast two-dimensional scanning with high angular precision over large scan angles, compact design and also high shock resistance. This is achieved with the combination of bulk silicon technology with metal surface micromachining. Besides medical diagnostics these microscanners can be used in a wider range of applications such as displays, two-dimensional barcode scanning, multiplexing of fiber optics, etc.

Optical MEMS is a challenging new field that combines micro- optics with micro-mechanics in order to build compact systems. In this paper we present a miniaturized Fourier transform spectrometer (FTS) fabricated on silicon. The FTS is a Michelson interferometer with one scanning mirror. The motion of the mirror is carried out by a new type of electrostatic comb drive actuator. The mirror is designed to be linear with respect to the applied voltage. Experimentally, we have measured a mirror displacement of 38.5 micrometer corresponding to a maximum optical path difference of 77 micrometer. The applied voltage was plus or minus 10 V and the non-linearity of the driving system is plus or minus 0.25 micrometer. A method is presented to correct the spectrum in order to get rid of the non-linearity. The measured resolution of the spectrometer after the phase correction is 16 nm at a wavelength of 633 nm.

Variable aberration compensation elements designed to correct the primary aberrations, and capable of sufficient speed for on-the-fly correction, can significantly extend the diffraction-limited field of view of scanned-beam instruments using practical microlens systems. In this paper we review the relevant aberration theory and discuss the requirements for compensation elements as well as appropriate architectures for correction of a scanned-beam instrument. We report correction of astigmatism and field curvature in an F/20 optical system using deformable polysilicon reflective membranes. Devices were successfully demonstrated that compensated more than 1.5 waves of defocus and more than 1 wave of astigmatism with less than 1/10 wave of spherical aberration, and with a bandwidth in excess of 20 kHz, which is suitable for high speed beam scanning applications such as video-rate imaging.

Within this paper novel applications of low temperature silicon wafer bonding technologies for the fabrication of high frequency silicon microscanners are presented. Two technological approaches are discussed, both using low temperature bonding as a key technological step. Results of the integration of a special low temperature bonding process within the bulk technology approach are shown. Micromirror arrays fabricated with this technology are presented and show promising results for optical applications.

This paper presents the design, fabrication, modeling, and testing of several Flexure-Beam Micromirror Device (FBMD) arrays fabricated using flip-chip assembly. These arrays were prefabricated using a silicon surface-micromachining technology and then transferred to a ceramic receiving substrate using a thin layer of indium placed between the bond pads of the two chips. Device characterization was completed using an interferometric microscope in which micromirror deflection was determined as a function of address potential. The arrays demonstrate reasonable micromirror performance with optically flat surfaces measuring only 5 - 6 nm of variance across as much as a 150 micrometer mirror surface.

This paper deals with micromirror arrays for high frequency applications. The use of monocrystalline silicon as mechanical material results in a low hysteresis, good reproducibility and high reliability. General characteristics, advantages and limitations of large analogously working mirror arrays in comparison with single elements will be discussed with respect to the requirements of desired applications. Special aspects of the design of micromirror arrays, experimental results concerning the behavior of the electromechanical system and optical properties will be presented as well. It will be shown that cascaded elements allow beside higher quality factors or resonant band width concerning the dynamic behavior also higher quasistatic deflection angles at diminished electrode gaps and lower driving voltages.

Lenslet integrated Micro-Electro-Mechanical Deformable Micromirrors (LMEM-DMs) are electrostatic micromirror arrays fabricated through a commercial surface micromachining process and integrated with polymer or glass microlenses. The electronics resins (Photo-BCB) which are photo-sensitive polymers were used to fabricate polymer microlens arrays. A 4 X 4 element photo-BCB Cyclotene microlens array was fabricated on a thin quartz substrate. Self-aligned soldering flip-chip assembly is applied to integrate microlens arrays directly over the micromirrors. The lens/mirror gap is controlled using the final height of solder balls, and the lateral alignment is achieved by the solder self-aligning mechanism. The LMEM-DM is attractive due to its low cost and the low drive voltages. The use of a lenslet to focus the incoming laser beam onto the reflective surface of a micromirror substantially increases overall optical fill factor of the micromirror array. The LMEM-DM provides superior aberration correction with low residual diffraction effects. For mirror deflections much smaller than the lenslet focal length, the LMEM-DM behaves as a phase-only modulating optical element. The LMEM-DM thus serves as a rugged, compact optical element for beam steering, beam shaping, and aberration correction applications.

We describe the reliability evaluation for MEMS devices, especially designed for DVD (Digital Video Disk) and CD compatible application module. These MEMS devices are fabricated as a mirror plane (shutter plane) used in DVD or CD data picking up. This micromachined annular shutter mirror (ASM) acts as an adjusting means of the numerical aperture. The electrostatic force can drive the upper plane up and down for focusing or defocusing of incident laser beam to the selected recording plane. So we need to evaluate the micromechanical properties of thin film structural materials to ensure the reliability of those MEMS devices. For those, we perform the fatigue tests onto the devices in the conditions of much accelerated than those of normal driving. The applied electrostatic force can induce the change of the thin film properties, and those are observed by direct and indirect methods. And then, we compare the fatigue effects with electrical, optical data from the intentionally-fatigue- applied specimen and as-fabricated one under accelerated conditions. Microstructure changes are able to explain the fatigue effects through observing the crack initiation, propagation, and its size around stress concentration region of metal mirror plane. Consequently, we can estimate the structural reliability and will provide the effective suggestion data for the fabrication of stable mirror material before commercialization.

A surface-micromachined plate-type actuator with two torsional support beams has been developed for optical applications. A silicon-nitride plate with an area of 1 X 1 mm2 is electroplated with a soft magnetic material (permalloy) and can be activated by an external magnetic field. In order to deflect the mirror to a very large angle, the geometry of the beams has been optimized using numerical simulation and theoretical analysis. Experimental data showed that the micro mirror is robust enough to be rotated up to 180 degrees over 10,000 times without any damage. The mirror is demonstrated as a laser beam deflector in this study. The deflection angle of the mirror can be controlled by the rotation of a permanent magnet. Data showed that this mirror could be rotated up to 90 degrees with a maximum frequency of 20 Hz. Details including design, fabrication, analysis, as well as operation, have been presented. Results showed that the device could be used as a scanning mirror for future application.

A compact polysilicon surface-micromachined microactuator designed for optical switching applications is described. This actuator is fabricated using the foundry MUMPs process provided by Cronos Integrated Microsystems Inc. Actuated electrothermally, the microactuator allows fast switching speeds and can be operated with a low voltage square-wave signal. The design, operation mechanisms for this long-range and high frequency thermal actuation are described. A vertical micromirror integrated with this actuator can be operated with a 10.5 V, 20 kHz 15% duty-cycle pulse signal, achieving a lateral moving speed higher than 15.6 mm/sec. The optical switch has been operated to frequencies as high as 30 kHz.

Optical fiber arrays have been proposed for signal paths in various civilian and military controls as a means of offering advanced sensing functions not available in electronic systems. To implement optic fiber sensors on various control systems, a proper electro-optic architecture (EOA) with a bar- coded electro-optical switch needs to be studied. In this paper, a design of such EO switch is proposed which can be operated remotely. Lithium Niobate is chosen as the EO material. The MEMS-IDT device is designed with Lithium Niobate as a substrate with IDT and a set of floating reflectors. The reflectors can be programmable and thus a bar-coded switch can be fabricated. The electrostatic field between the reflectors and the Lithium Niobate serves as the fast acting switch in this application.

We have developed different concepts of fiber optic switches based on hybrid transmittive micro-optical system, where switching is achieved by piezoelectrical movement of one of the micro-optical components. The input fiber beam is either collimated and deflected by a piezoelectrically driven short focal length microlens or refocussed onto a microprism structure, which is also piezoelectrically driven and deflects the beam in a number of discrete directions. In all of our configurations after deflection the beam is redirected and coupled into one of N output fibers by the use of a microlens array. The output fibers are also arranged in regular array. The switch configuration with continuous deflection is ideally suited for a large number of output channels, however, the problem still unsolved is to achieve high output channel stability and reproducibility. At the opposite, the discrete beam deflection approach ensures high stability and reproducibility by the optical arrangement and does not require position sensing for the actuators. The latter concept, of course requires special microprism elements, which are not available commercially. They have been fabricated with sufficient high quality by gray-tone lithography. For both concepts switch prototypes have been built up, yielding excellent optical parameters with respect to insertion loss and cross-talk. Typical switching times of 1 ms have been achieved. Special experimental setups have been built up for system integration.

In recent years, microspectrometers made by the LIGA technology for the visible wavelength range have found their way into the market. Opening the wide field of spectral analysis in the infrared range, the concept of a highly transmissive hollow waveguide has been demonstrated successfully. In combination with linear detector arrays, hollow waveguide microspectrometers can be combined into handheld infrared spectrometer systems. The only obstacle to a miniaturized system is the lack of miniaturized light modulators. To solve this problem, a miniaturized light modulator has been developed. It consists of an oscillating stop driven by an electromagnetic actuator. It is made out of permalloy by means of LIGA micromechanics. Its outer dimensions of approx. 3.0 X 3.2 mm2 and a structure height of 280 micrometer allow it to be integrated into the plane of the entrance slit of the microspectrometer of about 20 mm to 30 mm size. The spectrometer has alignment structures to ensure positioning of the oscillating stop close to the entrance slit. This simplifies assembly. The actuator is excited by an hybrid integrated coil fixed by springs snapping into place during assembly. The maximum supply voltage of 5V allows the chopper to be used in low-voltage spectrometer systems, especially in handheld systems. The highest modulation frequency is more than 1 kHz, which is sufficient to work with the lead salt detectors commonly used. In this frequency range, detector noise is greatly attenuated compared to continuous-light operation. The paper contains an outline of the concept of the whole microspectrometer system. Experimental results are discussed to demonstrate the performance of the system.

Micro-optical slits and apertures are essential components of optical systems. As new devices addressable micro slit arrays are presented. These arrays act as spatial light modulator, scanner or optical shutter. It is discussed the microfabrication of chips with slits, new arrangements of actuators to address the slit as well as addressable micro slit array concepts. The microfabrication of chips is based on silicon membranes. By bulk micromachining technology very stable membranes of a thickness of 1.5 ... 2 micrometer are prepared. The dimensions of the slits are width 3 micrometer ... 1 mm, height up to 2 mm. They are prepared on a membrane area up to 1000 mm2. So it is possible to prepare a lot of slits, a slit array have up to 150 apertures. The slits are addressable by a linear shift of a piezoactuator. Concepts, features and limits of newly developed miniaturized piezoactuator devices with solid state links for slit-chips are given. The position can be controlled by an integrated path measurement system. Addressable architectures are made by two membrane and one membrane arrangements. An advantage is the very limited stray light compared with micromirror arrays and DMDs. The slit arrays are usable in the full spectral region. The development of the presented micro electro mechanical device is driven by the commercial applications of high performance spectral instruments. Features of the presented device are for example the spectral resolution advantage (up to the factor of 7) and the throughput advantage (up to the factor of 10) for the instrument.

A light modulation system based on microactuators array is reported. Electrostatically driven microstructures can close or open parts of a transparent substrate (glass in the visible range) modulating the incident light. The surface of the microstructures can be used as shutter or as mirror or simultaneously in both functions. Each microactuator of the array is made by three main parts: a rigid electrode coated on the substrate, a dielectric layer and a flexible electrode (cantilever). The flexible electrode is fixed at one end on the dielectric: elastic forces keep the cantilever suspended. The substrate and the rigid electrode are transparent. Applying an appropriate voltage between the electrodes, the flexible one changes its position, rolling on the surface of the dielectric. The previous transparent area becomes reflective. Photolithography and thin film technologies have been used to build microshutter-micromirror arrays. Preliminary electrical and optical tests are presented in this paper.

It has been shown that it is possible to produce highly selective and continuously tunable filters based on InP material using surface micro-machining. One interesting issue for this kind of device is NIR absorption spectroscopy for gas analysis. In this work, we present the design of a Resonant Cavity Enhanced tunable photodiode for operation around 1.6 micrometer near the C-H stretching frequency for organic molecules such as benzene. For this type of application, the required performances are a large tunability, a high selectivity, a weak temperature dependence and a constant absorption level over the tuning range. To meet these requirements the micro-system must be optimized from the optical and mechanical point of view. The RCE photodiode structure is composed of an air/InP bottom Bragg mirror and a dielectric top Bragg mirror. The cavity includes an air-gap and the InP layer containing a p.i.n. photodiode with absorption in a few strained InGaAs Quantum Wells (QWs). Tuning is obtained by actuating electrostatically the air micro-cavity thickness. A prospective device meeting the optical requirements has been designed. It is based on an absorption region composed of three InGaAS QWs conveniently located in the cavity standing wave pattern in order to optimize the resonant absorption over the tuning range. Optical simulation shows that an absorption level greater than 50% can be achieved. The temperature dependence of the resonance wavelength can be kept below 0.08 nm/(Delta) T(C degrees) at room temperature. The mechanical properties of the micromachined structure has been investigated using finite element analysis.

We describe the design and microfabrication of an extremely compact optical system as a key element in an integrated capillary-channel electrochromatograph with laser induced fluorescence detection. The optical design uses substrate-mode propagation within the fused silica substrate. The optical system includes a vertical cavity surface-emitting laser (VCSEL) array, two high performance microlenses and a commercial photodetector. The microlenses are multilevel diffractive optics patterned by electron beam lithography and etched by reactive ion etching in fused silica. Two generations of optical subsystems are described. The first generation design is integrated directly onto the capillary channel-containing substrate with a 6 mm separation between the VCSEL and photodetector. The second generation design separates the optical system onto its own module and the source to detector length is further compressed to 3.5 mm. The systems are designed for indirect fluorescence detection using infrared dyes. The first generation design has been tested with a 750 nm VCSEL exciting a 10-4 M solution of CY-7 dye. The observed signal-to-noise ratio of better than 100:1 demonstrates that the background signal from scattered pump light is low despite the compact size of the optical system and meets the system sensitivity requirements.

IntelliSense Corporation has designed, fabricated, and tested a chemical and biological sensor based on MOEM technology. The sensor is based on novel integrated optic technology. Data collected from the prototype device indicates sensor sensitivity at least three order of magnitude higher than conventional Mack Zhender interferometers. The application specific sensor can be used for single and multi-analyte detection. The design combines a sensing waveguide and a microfabricated fluid delivery system. This integration permits analyte samples to be transported to a reaction well in contact with the sensing surface. In the reaction well, immobilized reagents react with the analyte, changing the optical properties of the waveguide surface. Measuring this change for an array of reaction wells, the sensor selectively identifies the composition and concentration of test substances. The novel sensing technology is based on pairs of MOEM optical waveguides. For the tests conducted, laser light was coupled into the waveguides, and measured. Because the evanescent field of the propagating light penetrated the waveguide surface, the coupled light was affected by the waveguide surface. Changes in the waveguide surface created by analyte-reagent bonding were measured. Sensors based on the developed technology provide low cost, small, sensitive, and selective sensing solutions for chemical and biological applications.

We developed a micro optical scanning sensor with the dimension of 2.0 mm X 4.0 mm X 3.0 mm for a micro inspection robot. In this sensor, the functional elements such as a laser diode (light source), photo diodes, pin-holes, a beam splitter, a ball lens, and a PZT thin film actuator driven micro optical scanner are integrated on separate substrates each consisting a functional modules and the substrates are stacked. Performance of the optical sensor depends on its optical characteristics. This sensor has spot size of output beam is 256 micrometer X 580 micrometer at 60 mm from the sensor, output power is 0.5 mW, optical scanning angles are plus or minus 10 deg. two-dimensionally, and detecting sensitivity of photo diodes are 0.3 A/W. The sensor is capable of distance measurement between the sensor and an object at 50 mm plus or minus 10 mm and the object shape recognition two-dimensionally based on the optical scanning method. By using these functions, the sensor can measure dimensions of the object and measuring resolution is less than 0.5 mm.

We discuss an optical reflection technique to sense very small variations of the refractive index that can be applied to absorbing and non-homogeneous media. The technique offers the possibility of being integrated, using MOEMS technology into a compact optical probe for a variety of applications, and may be the core for a new class of generic sensors. It consists of AC-modulating the angle of incidence near the critical angle and measuring the reflectivity variations. This technique may be a useful alternative to design a refractive index probe for absorbing and inhomogeneous media were other techniques are strongly limited. The theory necessary to use, develop, and design appropriately these kind of sensors is summarized, and experimental results validating the theory are given. A possible design of a fiber-optic probe based on the modulation of the index of refraction of a micro-prism through the elasto-optic effect is given.

Three different types of deformable mirror Spatial Light Modulators (SLMs) based on device concepts like Viscoelastic Control Layer (VCL), Cantilever Beam Mirror (CBM), and Moving Liquid Mirror (MLM) have been developed. All of them allow to create deformation profiles which act as phase gratings whose period is defined by the pitch of the pixel electrodes. The diffraction of the incident light is used to achieve spatial light modulation. The operation principles of the different types of SLMs are outlined in detail. All the mentioned SLMs can be manufactured on top of a high voltage CMOS circuitry. SLMs with up to 2 million pixels in analog operation mode have been realized up to now. The benefits of the different approaches with respect to fabrication aspects and respect to different applications will be addressed. For the angular deflection of light a new type of resonant microscanner mirror was developed. The device is based on a silicon micromechanical torsional actuator. The new approach for the configuration of the electrodes and the resulting driving principle allows to achieve large scanning angles (plus or minus 30 degree optically at atmospheric pressure) at low driving voltages (20 V max.) and low power consumption (less than 1 (mu) W). The operation principle of the new device enables the realization of 2D scanners as well.

MicroOptoElectroMechanical (MOEM) devices include both the application of micromechanics to control micro-optical systems and the application of micro-optical systems to provide monitoring and feedback for micromechanical systems. This paper presents microsystem applications at Sandia National Laboratories that require the integration of micromechanics with transmissive and reflective micro-optical systems to achieve specific functions. The goal of the presentation is to provide 'system pull' by discussing the enhanced functionality of MOEMS. In particular, this paper describes MOEM systems based on polycrystalline silicon sacrificial Surface MicroMachining (SMM) devices. In one example, an environmental sensor, a Gallium Arsenide (GaAs) Photonic Integrated Circuit (PIC) is assembled with an SMM device and an Application- Specific Integrated Circuit (ASIC) to achieve a specific function. The PIC is used to monitor the SMM device. The PIC output is processed by the ASIC to generate a specific signal. The second system illustrates the micromechanical control of an optical beam. This system consists of an SMM shutter device that has been post-processed using High Aspect Ratio Silicon Etching (HARSE) to accept a Vertical Cavity Surface Emitting Laser (VCSEL). Another system in the early stages of development is an SMM mechanical timer, which illustrates the need for the development of compact, multi-channel micro- optical monitoring technologies.

In this paper we demonstrate the use of diffractive gratings to optically measure strain in miniature ultrasonic transducers. Aluminum diffraction gratings were fabricated on silicon-microfabricated ultrasonic horns and beams which were actuated by bonded piezoelectric PZT (Lead-Zirconate Titanate) plates. A He-Ne laser beam was diffracted from the grating and a knife-edge was used to measure small changes in the diffraction angle as a result of time varying grating space and width. The measured strain and displacement profiles agreed with the expected mode patterns for the silicon resonators.

Micromachine accelerometers offer a way to enable critical functions only when a system encounters a particular acceleration environment. This paper describes the optical readout of a surface micromachine accelerometer containing a unique 24-bit code. The readout uses waveguide-based optics, which are implemented as a photonic integrated circuit (PIC). The PIC is flip-chip bonded over the micromachine, for a compact package. The shuttle moves 500 micrometer during readout, and each code element is 17 micrometer wide. The particular readout scheme makes use of backscattered radiation from etched features in the accelerometer shuttle. The features are etched to create corner reflectors that return radiation back toward the source for a 'one' bit. For a 'zero' bit, the shuttle is not etched, and the radiation scatters forward, away from the detector. This arrangement provides a large signal difference between a 'one' and 'zero' signal, since the 'zero' signal returns virtually no signal to the detector. It is thus superior to schemes that interrogate the code vertically, which have a limited contrast between a 'one' and a 'zero.' Experimental results are presented for mock shuttle features etched into a silicon substrate. To simulate the shuttle moving under a fixed PIC, a commercially available waveguide source was scanned over the mock code.

The technology of microelectronics that has evolved over the past half century is one of great power and sophistication and can now be extended to many applications (MEMS and MOEMS) other than electronics. An interesting application of MEMS quantum devices is the detection of electromagnetic radiation. The operation principle of MEMS quantum devices is based on the photoinduced stress in semiconductors, and the photon detection results from the measurement of the photoinduced bending. These devices can be described as micromechanical photon detectors. In this work, we have developed a technique for simulating electronic stresses using finite element analysis. We have used our technique to model the response of micromechanical photon devices to external stimuli and compared these results with experimental data. Material properties, geometry, and bimaterial design play an important role in the performance of micromechanical photon detectors. We have modeled these effects using finite element analysis and included the effects of bimaterial thickness coating, effective length of the device, width, and thickness.

Infrared micromirror arrays with large pixel size and large deflection angle have been fabricated and characterized. The paper presents the technology for the realization of micromirror arrays up to 1282 elements, which have both, a pixel size of 100 micrometer X 100 micrometer and a mirror tilting angle of plus or minus 15 degrees. This specification requires an approx. 13 micrometer gap for electrostatic actuation. A metal surface micromachining process has been developed using thick resist UV-lithography, multiple electroplating, a copper sacrificial layer and a CMP process step. Using nonplanar electrodes the driving voltage of electrostatic actuators can be reduced by factors. Using an electrical biasing concept the address voltage could be reduced further. A double layer metalization makes single mirror addressing within the array possible. Applicable switching times and the motion behavior will be discussed using measurement data of a vibrometer.

Closed-loop MEMS control enables mechanical microsystems to adapt to the demands of the environment which they are actuating opening a new window of opportunity for future MEMS applications. Planar diffractive optical microsystems have the potential to enable the integrated optical interrogation of MEMS microstructure position fully decoupled from the means of mechanical actuation which is central to realization of feedback control. This paper presents the results of initial research evaluating through-wafer optical microsystems for MEMS integrated optical monitoring. Positional monitoring results obtained from a 1.3 micrometer wavelength through- wafer free-space optical probe of a lateral comb resonator fabricated using the Multi-User MEMS Process Service (MUMPS) are presented. Given the availability of positional information via probe signal feedback, a simulation of the application of nonlinear sliding control is presented illustrating position control of the lateral comb resonator structure.

The novel thermal image system described in this paper is an all-light-processing infrared image transducer based on micromachining technology. This system incorporates the function of infrared image conversion and image intensification together on the base of a light-modulating thermal image device (LMTID), a monolithically fabricated chip using CMOS compatible surface micromachining techniques. This system has a series of potential advantages: high sensitivity and definition, low volume and power expenditure as well as short response time and room temperature operating ability. The design and modeling of the device are presented. Theoretical calculations on the sensitivity, minimum detectable power, and response time are carried out using a simple beam theory, and the design is optimized for the sake of high sensitivity and low minimum detectable power. FEM simulation using ANSYS 5.4 program basically demonstrates the theoretical calculations, as a result of which a sensitivity of 0.03 m/W and a response time of 6 ms are obtained.

We have built a miniature illuminator for Laser Doppler velocimeter on micromachined silicon optical bench utilizing a novel optical scheme. We used two intersecting coherent beams from the two opposing facets of semiconductor laser die to form a standing interference pattern needed for the particle detection and velocity measurement. Such devices are of interest to NASA for investigating wind patterns and dust loading on planets with atmosphere. They have been applied to problems where the liquid or gas flux must be characterized without disturbing the flow. In addition, the small probe volume makes possible local flow characterization and profiling. The device fabrication, and the results of the fringe characterization and velocity measurements are presented and discussed.

The ultimate goal of this project is to develop a manipulation system enabling unskilled operators to deal with objects in micron or sub-micron size as easily as to deal with objects in usual size. Described in this paper is the results achieved in the first phase of the research, in which the focusing point is given to the conceptual design, the prototype development and the operability evaluation. The system is modularized into the manipulation unit, the control unit and the man-machine interface. The manipulation unit is further comprised of a twin-arm manipulator mounted on a rotary table and a specimen stage with four degrees of freedom linear along X, Y and Z direction, and rotational around the Z-axis. The manipulator is driven by PZT actuators with magnifier elements and able to cover an envelope as wide a 200 micrometer for each axis of X, Y and Z. Instead of doing a direct operation, the operator steers the manipulator via an user-friendly interface which is designed to absorb the optical and mechanical variations. It allows the operator to concentrate to the manipulation without paying mach attentions to the changes in magnification of SEM or other conditions. The control unit merges the visual information of the SEM and the manipulation information from the user interface and derives the optimum locomotion of the arm for the desired operation.

Sandia National Laboratories is developing a MEMS-based trajectory safety subsystem, which allows enablement of critical functions only after a particular acceleration environment has been achieved. The device, known as an Environmental Sensing Device (ESD), consists of a suspended moving shuttle that translates a given distance when exposed to an appropriate acceleration environment. The shuttle contains an embedded code, consisting of grating structures, hat is illuminated and optically read using a semiconductor laser and detector integrated together in a GaAs-based Photonic Integrated Circuit (PIC) flip-chip bonded to the assembly. This paper will describe the optical design and performance analysis of the embedded code features in the shuttle.

The use of amorphous silicon solar cell array high voltage power source as an on-demand wireless power source for electrostatically actuated 32 X 32 micromirror array is presented. The amorphous silicon solar cell array has been reported previously by authors of this paper. In this work, the solar cell array has been used to drive distributed electrostatic actuator array (micromirror array in this particular paper). A 32 X 32 micromirror array has been fabricated and the size of single micromirror is 200 micrometer X 200 micrometer. Static deflection test of micromirrors has been carried out and pull-in voltage of 44 V and releasing voltage of 30 V was found. The electrical output of the solar cell array has been directly connected to the 32 X 32 micromirror array to demonstrate a wireless powered distributed MEMS actuator array. A total solar cell array area of 0.3 cm2 (30 series-interconnected solar cells) were used to drive a part of 32 X 32 micromirror array (a total array area of 0.4 cm2). Motion of multiple numbers of micromirrors was reproducibly observed. The ultimate goal of this research is to achieve power-integrated autonomous MEMS using solar cell array as a miniaturized wireless on-board power source and distributed actuator array as a locomotive engine.

A novel optical interferometer based on detecting the standing wave is described. The key device is a newly developed ultra- thin Si photodetector. The active layer of the ultra-thin photodetector is thinner than a half of wavelength of the incident light. Only a small part of the incident light is detected and the rest passes through the ultra-thin photodetector before being absorbed. Being inserted in the optical field, this ultra-thin photodetector can detect the thin intensity profile formed along the propagating direction of the laser beam. Taking advantage of this function, we have realized the vertical construction of a new interferometer detecting standing wave and the waveguide is not used, leading to the possibilities to achieve the integration of the interferometer by stacking planar components layer by layer and to array many interferometers together. The design, fabrication, and operation of this displacement sensor are discussed. The measured interference signal confirms the feasibility of the new sensor system. For one example of the arrayed interferometer, the dual ultra-thin Si photodetector is also fabricated with a phase shifter, and the displacement direction can be detected by comparing the phase of the two signals.

A new type all optical vibration and acceleration sensor using the combination of micromachined Si cantilever and optical fiber is proposed, and its fundamental characteristics are demonstrated. The light emitted from bulb-lens set into the V- groove is reflected at the reflector formed on the Si cantilever and then recoupled into the bulb-lens. Several sensors with different length (0.64 - 6.0 mm long) of the Si cantilever are fabricated to compare the theoretical resonance frequency fr obtained from the simple model and experimental ones. They had good agreement. From the sensing principle the sensing frequency range of the vibration is suitable below the fr of the Si cantilever of the sensor.

In this paper we analyze the effect of the laser beam divergence on the sensitivity of optical sensors based on surface plasmon resonance (SPR) using the Kretschmann configuration. The analysis is done by assuming that a Gaussian beam is employed. Numerical results are presented that show quantitatively the influence of the laser beam's waist on the SPR curve main characteristics. An example using the exact Fresnel coefficient, with optimal parameters reported in the literature is fully analyzed. Our results may be important in the design of SPR optical sensors using fiber or integrated optics.

Five types of micromirror arrays were designed and fabricated using a three-level, polysilicon, surface micromachined, micro-electromechanical systems (MEMS) process. The electrostatically deflectable micromirror designs included arrays of simple cantilever beams, torsion beams, tethered (piston-style) beams, circular membranes, and oval membranes. The smallest micromirror element was the simple cantilever beam, measuring 50 micrometer square. The largest micromirror element was the oval membrane; it possessed an active optical surface that was 320 micrometer by 920 micrometer. Each of the remaining micromirror designs have gold-coated polysilicon optical surfaces with geometries between these two limits. Electrostatically induced vertical deflections on the order of 2.75 micrometer were achieved. The torsion beam micromirror design exhibits both in-plane and out-of-plane deflection. The other micromirror designs only manifest in-plane deflections. The modeling phase focused on the microdynamical behavior of the torsion beam micromirror. The IntelliCADR finite element analysis program was used to generate a plot of the micromirror's deflection (d) versus applied direct current voltage (V). The data was least-squares fitted to the well- established V varies direct as d3/2 relationship. A resonant frequency analysis predicted an approximate switching speed of 6 microseconds. The reliability (number of operational cycles) of each micromirror design, when operated with a rectified 60 Hz alternating current (ac) signal, was measured to exceed more than 1 million flexure events. Experimental evidence supporting the potential for using micromirrors as binary optical switches and amplitude modulators is also addressed.

A novel self-aligning silicon optical bench for fully passive alignment of optical components and its fabrication method are presented. Key technologies developed in this work are multi- step silicon anisotropic etching for manufacturing SiOB, photolithography on three-dimensional surface, precise size control of optical active chip, and flux- and pressure-free die bonding technology. The measured size tolerance of silicon grooves for the active chip and the fiber reveals less than plus or minus 0.5 micrometer. The photolithography process on three-dimensional surface of each site is investigated to get the patterns for deposition of electrodes, mirror, and solders, respectively. The precisely cleaved laser diode chip is obtained by V-groove etching to define the cleaving lane. This technique allows the chip to be defined with a dimensional accuracy of plus or minus 0.5 micrometer. In addition, the pressure-free bonding technique using the electroplated Au-Sn solder makes it possible to reduce the production cost. The fabricated SiOB does not need any pre- alignment process of the optical chip and fiber to desired position such as index alignment method. On the basis of these technologies, it is shown that the fully passive alignment of optical component packaging is successfully preformed. The measured results reveal that the coupling efficiency of the laser diode module was achieved better than 8% and the responsivity of the photo diode module was better than 0.85 A/W.

In building the movable elements of robots, peripheral devices and measuring apparata, increasing the resolution of the angular sensor systems, based on incremental rotary encoders, is essential, together with decreasing the complexity, dimensions and weight. Especially when the angular sensor is integrated in a measuring system, belonging to a programmed light airplane for surveillance, the key issue is to reduce both dimensions and weight. This can be done using a simplified design, which consists in the following solutions: replacement of the fragile Cr on glass substrate, 1.5 mm thick (normally used for the fabrication of incremental disks), with light Cr on polycarbonate substrate, with only 0.15 mm thick; the absence of collimating optics (based on microlenses, used in IR emitter-photocell receiver assembly), as a result of the good coupling efficiency (due to the possible approaching of these elements at minimum 0.45 mm); the shrinkage of the disk's diameters to only 14 mm; the use of surface mounting devices and the related surface mounting technology, enabling to reduce dimensions and weight. The maximum number of slits on a 14 mm diameter dividing disk, usually obtained in a Cr on polycarbonate version, being approx. 1000, no problem occurs in our case, for 360 slits. The requested angular resolution (only 0.5 degrees for the light airplane), using the whole classical '4x digital multiplication' is not necessary, but a lower one of only 2x, resulting in a simplified electronics. The proposed design permitted, that an original arrangement, for building a small size, lightweight, heavy-duty incremental transducer based angular sensor system, to be obtained, useful not only in avionics, but also in robotics, or other special applications. Besides, extending the number of fixed gratings (masks) allows, that many primary signals to be derived, and a further increase in resolution of even 6 angular minutes to be obtained from the initial 360 slits.

We are developing a two-dimensional array of microshutters which can be used as a high efficiency, high contrast field selection device for a multi-object spectrometer for the Next Generation Space Telescope (NGST). The device is a close- packed array of shutters, with a typical size of 100 microns square and area filling factor of up to 80%. Each shutter, made of single crystal silicon with an appropriate optical coating, pivots on a torsion flexure along one edge. Each of the shutters is individually selectable. An original double- shutter mechanism is employed for actuation. Since the device works in transmission, there is no loss of contrast due to diffraction from the edges of unactuated pixels. When working in reflection, the device can also be used as a micromirror array.

An integrated silicon sub-mount for laser diodes is reported. The objective of this work is to develop a miniaturized laser source module with switchable wavelengths to use a common optics for different optical data storage media. Patterned thick photoresist: SU-8 is adopted as a micromirror structure in conjunction with proper mirror coating with thin metal film. Photolithographically defined and pre-aligned micromirrors potentially offer an enhanced degree of freedom to optical MEMS designer and greatly reduce the misalignment errors in assembling the optical components. Mesa-shaped mounting seats for assembling the laser diodes, tall vertical sidewall mirrors for reflecting the laser beams emitted from the laser diodes, and deep trench not to disturb the reflected laser beams are integrated on a silicon sub-mount chip by micromachining. The average surface roughness of the metal coated SU-8 sidewall mirrors is well below 1/20 wavelength of the incident laser light of interest, smooth enough for CD or DVD applications. The insertion loss of the vertical sidewall mirror is measured as -0.77 dB when the wavelength of the reflected laser beam is 650 nm.

We have observed the effects of electrical charging in the Mechanical Anti-Reflection Switch (MARS) device for some time. The MARS device has a membrane that is pulled toward the substrate by application of an electrical bias, and thereby produces optical modulation. Under constant bias MARS devices with insulating membranes exhibit a slow (minutes to hours) change in air gap. We have now determined that this is due to ionization in the air gap, and that the effect can be greatly reduced by placing the device in an argon atmosphere. It is postulated that the effect is due to the formation of a space charge region in the air gap adjacent to the membrane.

Liquid crystal over silicon (LCoS) is an established technology for reflective spatial light modulators (SLM's) and microdisplays. While most of the manufacturing methods used are mature, there exist a number of unresolved issues associated with the mass production of high quality devices. Existing manufacturing technology leaves the final mirror elements raised from the surface of the surrounding dielectric causing problems with the filling of the liquid crystal (LC). The flow front during filling is influential on the final alignment qualities, so it is essential that this flow front follows the ideal linear shape. We report on a method to remove this mirror step height by the use of an aluminum dual damascene technique. This process produces mirrors which are embedded within the dielectric insulating layer thereby removing most of the LC flow front aberrations, caused by the surface topography, during LC filling. We discuss the novel methods developed to overcome the damascene induced problems of dishing and erosion. The results will be discussed with particular bias towards their use in the manufacture of reflective micro-displays.

There is a growing need for micro-optical components in the field of tele- and datacom applications. Such components have to be very precise and should be available in reasonable numbers. Microtechnology provides manufacturing techniques that fulfill both requirements. Using micro electro discharge machining, laser micromachining, ultra precision milling and deep lithography with subsequent electroforming methods, complex tools for the replication of highly precise plastic parts have been manufactured. In many cases a combination of methods enumerated above gives a tool which shows both functionality and cost-efficiency. As examples we present the realization of integrated-optical components with passive fiber-waveguide coupling used as components in optical networks and as velocity sensors for two-phase flows, like liquids containing small gas bubbles or particles. In the first case multimode 4 X 4 star couplers have been manufactured in a pilot series that show excess loss values below 3 dB and a uniformity better than 3 dB at 830 nm. This performance becomes possible by using a compression molding process. By stamping the microstructured mold into a semifinished PMMA plate exact replication of the molds as well as very low surface roughness of the waveguide side walls could be observed. In the second case the waveguide channels of the flow sensors show dimensions of between 20 micrometer and 100 micrometer and an aspect ratio of about 20. These structures have been replicated by injection molding of PMMA using variotherm process treatment with a cycle time of about 2 - 3 min.